TVRD receiver system with automatic bandwidth adjustment

• US 4,792,993 A
• Filed: 10/30/1985
• Issued: 12/20/1988
• Est. Priority Date: 10/30/1985
• Status: Expired due to Fees

• Current Assignee: Astec International Limited (Emerson Electric Company)
• Original Assignee: Capetronic Group Ltd. (Nimble Holdings Co. Ltd.)
• Inventors: Ma, John Y.
• Primary Examiner(s): Griffin, Robert L.
• Assistant Examiner(s): Kuntz, Curtis
• Application Number:
  US06/792,783
• Time in Patent Office: 1,147 Days
• Field of Search: 455/188, 455/189, 455/190, 455/191, 455/200, 455/266, 455/339, 455/340, 358/193.1
• US Class Current: 455/266
• CPC Class Codes: H03J 1/16 Single control means independently performing two or more functions

Abstract

An improved TVRO receiver for receiving signals broadcast over a plurality of channels with varying bandwidths and having a tuner producing output signals corresponding to the received signals and having bandwidths which vary from channel to channel is provided with a band pass filtering arrangement receiving the output signals and having a controllably adjustable pass band, a bandwidth detection circuit for receiving the output signals passing through the filtering arrangement and being responsive to a current output signal corresponding to the channel being received for producing a control signal indicative of the extent of deviation of the bandwidth of the current output signal beyond the current pass band of the filtering arrangement, and a control circuit responsive to the control signal for adjusting the pass band of the filtering arrangement to accommodate the bandwidth of the current output signal corresponding to the channel being received, if the bandwidth deviation of the current output signal exceeds a predetermined threshold value.

Claims

1. In a TVRO receiver for receiving signals broadcast over a plurality of channels with varying bandwidths and having a tuner producing output signals corresponding to selected ones of said received signals and having bandwidths which vary from channel to channel, the improvement comprising

bandpass filtering means receiving said output signals and having a controllably adjustable pass band,

bandwidth detecting means for receiving the output signals passing through said filtering means, said detecting means being responsive to a current output signal corresponding to the channel being received for producing a control signal indicative of the extent of deviation of the bandwidth of the current output signal beyond the current pass band of said filtering means, said control signal being substantially independent of the signal level of broadcast signals received by said tuner, and

control means responsive to said control signal for adjusting the pass band of said filtering means to accommodate the bandwidth of the current output signal corresponding to the channel being received, if the bandwidth deviation of said current output signal exceeds a predetermined threshold value.

2. The TVRO receiver of claim 1 wherein said tuner is fed by means provided in the receiver for receiving the broadcast signals and converting said signals to first IF signals, said tuner receiving and converting said 1st IF signals to a 2nd IF frequency range, demodulator means provided in the receiver for receiving said 2nd IF signals and producing output signals which vary in proportion to deviations in the frequency of said 2nd IF signals from the center frequency of said 2nd IF frequency range, said demodulator output signals being fed to said filtering means.

3. The TVRO receiver of claim 2 wherein the demodulator means produces output signals having peak levels proportional to the bandwidth of said 2nd IF signals received by the demodulator.

4. The TVRO receiver of claim 1 wherein said bandwidth detecting means includes a peak detector for producing said control signal in response to deviations of the current output signal beyond the passband of said filtering means.

5. The TVRO receiver of claim 4 wherein the control means includes means for adjusting the pass band of said filtering means in response to (1) a single deviation of said output signal beyond a first predetermined threshold outside the current pass band, or (2) repeated deviations of said output signal beyond a second predetermined threshold outside the current pass band, said second threshold being closer to the existing pass band than said first threshold.

6. The TVRO receiver of claim 1 which includes means for amplifying the output of said filtering means before it reaches said bandwidth detecting means, and means associated with said amplifying means for automatically adjusting the gain of said amplifying mean in response to said control signal from said bandwidth detecting means so as to maintain the amplitude of said output signal within a relatively constant range regardless of the width of the pass band of said filtering means.

7. The TVRO receiver of claim 1 which includes demodulator means for feeding said tuner and producing video and audio baseband signals corresponding to said received broadcast signals, and said tuner is an audio tuner receiving only said audio baseband signals form said demodulator means in order to produce said corresponding output signals.

8. The TVRO receiver of claim 7 wherein said audio tuner includes a superheterodyne circuit for converting the audio baseband signals to an audio IF frequency range, and a detector for detecting an audio signal at a prescribed audio IF frequency in the output of said superheterodyne circuit, said filtering means being located between said superheterodyne circuit and said detector, and said bandwidth detecting means receives the output of said detector.

9. A TVRO receiver as set forth in claim 1 wherein said filtering means comprises a plurality of IF passband filters for receiving signals having bandwidths which vary from channel to channel, said filters having pass bands of different widths, and said control means includes switching means associated with said filters and responsive to said control signal for feeding said output signals to a selected one of said filters having a pass band capable of accomodating the bandwidth of the current output signal.

10. In a TVRO receiver for receiving signals broadcast over a plurality of channels with varying bandwidths and having a tuner producing output signals corresponding to selected ones of said received signals and having bandwidths which vary from channel to channel, the improvement comprising

bandpass filtering means receiving said output signals and having a controllably adjustable pass band,

bandwidth detecting means for receiving the output signals passing through said filtering means, said detecting means being responsive to a current output signal corresponding to the channel being received for producing a control signal indicative of the extent of deviation of the bandwidth of the current output signal beyond the current pass band of said filtering means,

control means responsive to said control signal for adjusting the pass band of said filtering means to accommodate the bandwidth of the current output signal corresponding to the channel being received, if the bandwidth deviation of said current output signal exceeds a predetermined threshold value, and

means for amplifying the output of said filtering means before it reaches said bandwidth detecting means, and means associated with said amplifying means for automatically adjusting the gain of said amplifying means in response to said control signal from said bandwidth detecting means so as to maintain the amplitude of said output signal within a relatively constant range regardless of the width of the pass band of said filtering means.

11. In a TVRO receiver for receiving signals broadcast over a plurality of channels with varying bandwidths and having a tuner producing output signals corresponding to selected ones of said received signals and having bandwidths which vary from channel to channel, the improvement comprising

bandpass filtering means receiving said output signals and having a controllably adjustable pass band, said filtering means comprising a plurality of IF passband filters for receiving signals having bandwidths which vary from channel to channel, said filters having pass bands of different widths,

bandwidth detecting means for receiving the output signals passing through said filtering means, said detecting means being responsive to a current output signal corresponding to the channel being received for producing a control signal indicative of the extent of deviation of the bandwidth of the current output signal beyond the current pass band of said filtering means, and

control means responsive to said control signal for adjusting the pass band of said filtering means to accommodate the bandwidth of the current output signal corresponding to the channel being received, if the bandwidth deviation of said current output signals exceeds a predetermined threshold value, said control means including switching means associated with said filters and responsive to said control signal for feeding said output signals to a selected one of said filters having a passband corresponding to the bandwidth of the current output signal.

12. In a TVRO receiver for receiving signals broadcast over a plurality of channels with varying bandwidths and having a tuner producing output signals corresponding to selected ones of said received signals and having a bandwidths which vary from channel to channel, the improvement comprising

bandpass filtering means receiving said output signals and having a controllably adjustable pass band,

bandwidth detecting means for receiving the output signals passing through said filtering means, said detecting means including peak detection means responsive to a current output signal corresponding to the channel being received for producing a control signal indicative of the extent of deviation of the bandwidth of the current output signal beyond the current pass band of said filtering means,

control means responsive to said control signal for adjusting the pass band of said filtering means to accommodate the bandwidth of the current output signal corresponding to the channel being received, if the bandwidth deviation of said current output signal exceeds a predetermined threshold value, said control means including means for adjusting the pass band of said filtering means in response to (1) a signal deviation of said output signal beyond a first predetermined threshold outside the current pass band, or (2) repeated deviations of said output signal beyond a second predetermined threshold outside the current pass band, said second threshold being closer to the existing pass band than said first threshold.

13. In a TVRO receiver for receiving signals broadcast over a plurality of channels with varying bandwidths and having a tuner producing output signals corresponding to selected ones of said received siganls and having bandwidths which vary from channel to channel, said tuner being fed by means provided in the receiver for receiving the broadcast signals and converting said signals to first IF signals, said tuner receiving and converting said first IF signals to a second IF frequency range, demodulator means provided in the receiver for receiving said second IF signals and producing output signals which vary in proportion to deviations in the frequency of said second IF signals from the center frequency of said second IF frequency range, the improvement comprising

bandpass filtering means receiving said demodulator output signals and having a controllably adjustable pass band,

bandwidth detecting means for receiving the output signals passing through said filtering means, said detecting means being responsive to a current output signal corresponding to the channel being received for producing a control signal indicative of the extent of deviation of the bandwidth of the current output signal beyond the current pass band of said filtering means, and

control means responsive to said control signal for adjusting the pass band of said filtering means to accommodate the bandwidth of the current output signal corresponding to the channel being received, if the bandwidth deviation of said current output signal exceeds a predetermined threshold value.

14. The TVRO receiver of claim 13 wherein the demodulator means produces output signals having peak levels proportional to the bandwidth of said second IF signals received by the demodulator.

15. In a TVRO receiver for receiving signals broadcast over a plurality of channels with varying bandwidths and having demodulator means producing video and audio baseband signals corresponding to said received broadcast signals, an audio tuner for receiving the audio baseband signals from said demodulator means and producing output signals corresponding to selected ones of said received signals and having bandwidths which vary from channel to channel, the improvement comprising

bandpass filtering means receiving said output signals and having a controllably adjustable pass band,

bandwidth detecting means for receiving the output signals passing through said filtering means, said detecting means being responsive to a current output signal corresponding to the channel being received for producing a control signal indicative of the extent of deviation of the bandwidth of the current output signal beyond the current pass band of said filtering means, and

control means responsive to said control signal for adjusting the pass band of said filtering means to accommodate the bandwidth of the current output signal corresponding to the channel being received, if the band width deviation of said current output signal exceeds a predetermined threshold value.

16. The TVRO receiver of claim 15 wherein said audio tuner includes a superheterodyne circuit for converting the audio baseband signals to an audio IF frequency range, and a detector for detecting an audio signal at a prescribed audio IF frequency in the output of said superheterodyne circuit, said filtering means being located between said superheterodyne circuit and said detector, and said bandwidth detecting means receives the output of said detector.